Of the blazars detected by EGRET in GeV γ rays, 3C 279 is not only the best-observed by EGRET, but also one of the best-monitored at lower frequencies. We have assembled eleven spectra, from GHz radio through GeV γ rays, from the time intervals of EGRET observations. Although some of the data have appeared in previous publications, most are new, including data taken during the high states in early 1999 and early 2000. All of the spectra show substantial γ-ray contribution to the total luminosity of the object; in a high state, the γ-ray luminosity dominates over that at all other frequencies by a factor of more than 10. There is no clear pattern of time correlation; different bands do not always rise and fall together, even in the optical, X-ray, and γ-ray bands.The spectra are modeled using a leptonic jet, with combined synchrotron self-Compton + external Compton γ-ray production. Spectral variability of 3C 279 is consistent with variations of the bulk Lorentz factor of the jet, accompanied by changes in the spectral shape of the electron distribution. Our modeling results are consistent with the UV spectrum of 3C 279 being dominated by accretion disk radiation during times of low γ-ray intensity.Subject headings: quasars: individual (3C 279)

Abstract. Long term monitoring results from mid 1995 to the end of 2000 of quasar observations at 22, 37 and 87 GHz done at the Metsähovi radio observatory are presented. Approximately 15 700 observations are published here.

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Abstract. We present results of optical monitoring of quasars and blazars obtained at Tuorla Observatory between September 1995 and May 1997. The aim of our monitoring is to provide well sampled optical light curves for quasar and blazar studies. During the observing period the V -band brightness of S2 0109+224, 3C 66A, and ON 231 (W Comae) reached some of the brightest values ever measured for these objects. A strong outburst was observed in Mrk 421 and the large outburst, which was predicted earlier, in OJ 287 was confirmed. CTA 102 had over one magnitude outburst which happened in a timescale of a few days. For OI 090.4 we measured one of the faintest V -band brightness values ever.